The 'Tunnel Effect' in Rhesus Macaques
 
 
Here are some demonstrations of the various conditions discussed in the following paper:
Flombaum, J. I., Kundey, S. M., Santos, L. R., & Scholl, B. J. (2004). Dynamic object individuation in rhesus macaques: A study of the tunnel effect. Psychological Science, 15(12), 795-800.
These demonstrations are provided as Quicktime movies, which can be downloaded or viewed directly in most web-browsers. (To download a free Quicktime player, go here.) These movies are a bit large and choppy, but they should be sufficient to illustrate the basic conditions.  
 
Simultaneous Presentation Condition (16.6 MB)  
In this condition, the monkey sees both the lemon and the kiwi at the same time. After viewing this unambiguous spatiotemporal and featural evidence for two objects, most monkeys tended to search in both locations. This provides initial evidence that monkeys would search behind each occluder that they thought contained food.  
 
Temporal Gap With Feature Change Condition (33.7 MB)  
Individuation of two distinct objects based on only their featural differences was also observed in this condition, when the lemon and the kiwi were only seen successively. Here most monkeys also searched behind both occluders.  
 
Temporal Gap Without Feature Change Condition (63.7 MB)  
Searching both occluders clearly required the featural difference, however, since monkeys in this condition -- identical except that both food objects were lemons (or both kiwis) -- tended to search only behind Occluder 2.  
 
Tunnel Effect Condition (19.2 MB)  
This final condition provides evidence that monkeys perceive -- and act on the basis of -- the tunnel effect. This condition differed from the Temporal Gap With Feature Change condition only in that the kiwi appeared immediately after the disappearance of the lemon, yet monkeys now searched only behind Occluder 2 -- apparently perceiving the lemon transform into a kiwi on the basis of spatiotemporally continuous motion.